乙腈、3-乙氧基丙腈中水分含量检测方案(卡氏水分测定)

HITACHIInspire the Next 日立 HIRANUMAAPPLICATION DATA Karl Fischer Titrator Data No. KF7 Water contents Nitriles 1.Abstract Water content of Nitriles could be determined by Karl Fischer coulometric titrator. In coulometric titration，iodine of Karl Fischer reagent isgenerated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below. Nitriles do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with samplesolubility. General use of anode solution contain methanol as solvent. When the sample like a long chain hydrocarbon has poor solubility in methanol，anode solution containing chloroform or hexanol or toluene is used. 2. Apparatus and Reagents (1)Apparatus Titrator ：Hiranuma Karl Fischer Coulometric titrator AQ-series Electrolytic cell ：Standard Cell (2)Reagents Anode solution ：HYDRANAL Coulomat AG (Honeywell) Cathode solution ：HYDRANAL Coulomat CG (Honeywell) 3. Procedure Fill 100 mLof anode solution and one ampoule of cathode solution into the electrolytic cell as shown in Fig.3.1. When fritless cell is used， cathode solution is not (1) necessary. (2) Start blanking to attain stable background. (3) Wash the syringe with sample. (4) Draw the sample into syringe and then weigh the syringe. (5) Inject sample from rubber septum of electrolytic cell as shown in Fig.3.2. (6) Start titration. Measurement parameter is shown in Table 4.1. (7) Weigh the syringe again and then set the difference of weight to sample size. Fig.3.1. Preparation of the reagents. (Standard Cell) Fig.3.2. Injection of sample. 4. Parameters and results Table 4.1. Parameter. Condition File Cal Mode O：Sample weight(net) X=(H2O-BLANK)/SIZE Interval Time 20 sec Current SLOW S-Timer 0 min Blank Value 0 ug Unit Mode AUTO Auto Interval 0 g Minimum Count 5 pg Back Ground ON Sample Size Input Every Time Cell Type Standard/Fritless Table 4.2. Results of water content measurement in nitriles. Sample Cell Sample Water Water Content Statistics Results Size (g) (ug) (ppm) Acetonitrile Standard 1.5175 151.1 99.6 Avg. 99.3 ppm 1.5675 158.5 101.1 SD 2.0 ppm 1.5602 151.5 97.1 RSD 2.0% 3-Ethoxypropionitrile Standard 0.78380 255.4 325.8 Avg. 325.9 ppm 0.77352 253.0 327.1 SD 1.2 ppm 0.97904 318.0 324.8 RSD 0.4% 5.Note (1) Use dried syringe and syringe vial in Fig.5.1 for preventive of contamination by atmospheric water. To measure 100 ug or less water detection， make sure stability of blanking. Low and stable background value is important factor for trace level of water(2) measurement. Select anode solution according to the solubility of the sample. For example， Hydranal coulomat AG-H and Hydranal coulomat Oil are suitable for long chain(3) hydrocarbons and oil samples. The optimized electrolysis control for fritless cell of AQ series released after 2009 improves the measurement accuracy of fritless cell. It can be used with the(4) evaporator as well. Suitable reagent for fritless cell is required. For example， Hydranal coulomat AG and AG-Oven are compatible with fritless cell. FFig.5.1. Draw the sample from syringe vial. Keywords：KKarl Fischer， Coulometric titration， Direct injection， Nitrille， Fritless cell Science fora better tomorrow热线电话：立科学仪器(北京)有限公司 Science fora better tomorrow日立科学仪器(北京)有限公司热线电话： 本实验通过直接注入对腈类样品进行水含量的测定。